Transcript Sequencing
Scheduling
Introduction to Operations Management
1
What is scheduling
In
a production system, it is the timing
and sequencing of the use of specific
resources in the system and is the final
step in the decision making process of an
organization before the actual
transformation processes begin.
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Scheduling Manufacturing Operations
JAN
High-volume
FEB
MAR
APR
MAY
JUN
Build A
Intermediate-
A Done
volume
Low-volume
Service
operations
Build B
B Done
Build C
C Done
Build D
On time!
Ship
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High-Volume Systems
Flow
system: High-volume system with
Standardized equipment and activities
Flow-shop scheduling: Scheduling for
high-volume flow system
Work Center #1
Work Center #2
Output
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High-Volume Success Factors
Process
and product design
Preventive maintenance
Rapid repair when breakdown occurs
Optimal product mixes
Minimization of quality problems
Reliability and timing of supplies
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Intermediate-Volume Systems
Outputs
are between standardized highvolume systems and made-to-order job
shops
Economic run size:
2DS
p
Q0
H p u
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Scheduling Low-Volume Systems
Loading
- assignment of
jobs to process centers
Sequencing - determining
the order in which jobs will
be processed
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Loading
Gantt
chart - used as a visual aid for
loading and scheduling
Work
Mon. Tues.
Center
1
Job 3
2
Job 3
3
Job 1
4
Job 10
Wed.
Thurs.
Fri.
Job 4
Job 7
Job 6
Job 7
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Assignment Problem
Assigning jobs to workers. There is
a cost associated with a worker
completing a certain job. The
objective is to finish all the jobs by
the workers so that the total cost is
minimized.
Jobs
Workers
An optimal solution can be found
by the Hungarian
Method.
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Sequencing
Sequencing:
Determine the order in which
jobs at a work center will be processed.
Workstation: An
area where one person
works, usually with special equipment, on
a specialized job.
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Sequencing
Priority
rules: Simple heuristics
Everything is
used to select the order in
#1 Priority
which jobs will be processed.
Job
time: Time needed for
setup and processing of a job.
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Priority Rules
FCFS
SPT
DD
CR
S/O
Rush
- first come, first served
- shortest processing time
- due date
- critical ratio
- slack per operation
Top Priority
- emergency
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Two Work Center Sequencing
Johnson’s
Rule: technique for minimizing
completion time for a group of jobs to be
processed on two machines or at two
work centers.
Minimizes total idle time
Several conditions must be satisfied
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Johnson’s Rule Conditions
Job
time must be known and constant
Job times must be independent of
sequence
Jobs must follow same two-step sequence
Job priorities cannot be used
All units must be completed at the first
work center before moving to second
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Scheduling Service Operations
Appointment
systems
– Controls customer arrivals for service
Reservation
systems
– Estimates demand for service
Scheduling
the workforce
– Manages capacity for service
Scheduling
multiple resources
– Coordinates use of more than one resource
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Service Operation Problems
Cannot
store or inventory services
Customer service requests are random
Scheduling service involves
– Customers
– Workforce
– Equipment
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